This invention relates to multilamp photoflash units and, more particularly, to an improved cover configuration for preventing sympathetic flashing in compact multilamp photoflash units.
Sympathetic flashing, or ignition, is the terminology used for inadvertent ignition caused by a flashing lamp. Radiant energy from one lamp will fire another lamp if they are in close enough proximity. Multilamp photoflash units commonly available on the market to date have generally not posed a problem with respect to sympathetic flashing. One reason for this is due to the configuration of the array of reflectors associated with the lamps of a given unit. For example, in the units known as the flashcube, such as described in U.S. Pat. No. 3,327,105, and the magnitude, such as described in U.S. Pat. No. 3,730,669, four lamps are arranged behind respective light-transmitting reflecting sidewalls of a four sided enclosure, and an array of concave reflectors respectively associated with the lamps inherently blocks any direct radiation from one lamp to the other by virtue of physical configuration. The same holds true for the rivets referred to as a flashbar, such as described in U.S. Pat. No. b 3,857,667, wherein back-to-back horizontal reflector arrays of five lamps each face in opposite directions. Further, in certain embodiments of the units referred to as flipflash, a plurality of lamps are disposed in a planar array of concave refllectors which separate one lamp from another; an example of an eight-lamp array is described in U.S. Pat. No. 4,133,023, and an example of a ten-lamp array is described in U.S. Pat. No. 4,164,007.
Another reason contributing to minimization of the problem of sympathetic flashing is due to the size of the photoflash unit, and the orientation and spacing between lamps. For example, in the embodiment of a flipflash unit described in U.S. Pat. Nos. 3,894,226 and 3,937,946, for example, there are open spaces between adjacent lamps in a column. However, the comparatively larger spacing between lamps, and the fact that the lamps are oriented such that at least one and in some instances two press-seal bases intervene in the light path between lamps, makes the probability of sympathetic flashing quite insignificant.
Sympathetic flashing, however, can pose a problem where chemical photoflash lamps are densely packaged close to one another, particularly when reflectors are not used. Such is the case, for example, in U.S. Pat. Nos. 4,055,759, 4,070,145 and 4,076,488, wherein a plurality of percussively ignitable flashlamps are closely spaced in linear arrays for providing a hand actuated signal device. In this instance, the denoted patents describe the use of opaque partitions between adjacent lamps to prevent sympathetic ignition. In an example disclosed, each partition is a separate planar element wedged into a respective slot into a support member. It is also disclosed that a partition may have reflective surfaces.
A copending patent application Ser. No. 072,251 filed concurrently herewith and assigned to the present assignee, describes a more compact, cost-efficient photoflash unit construction comprising a linear array of electrically ignitable flashlamps mounted on a printed circuit board in the form of an elongated strip. The printed circuit strip is located within the longitudinal channel of an elongated housing member having reflective surfaces adjacent to the lamps. A light-transmitting cover panel is attached to the front of the housing member to enclose the flashlamps. The lamps have substantially tubular envelopes and are positioned extremely close to one another with their longitudinal axes substantially parallel to a surface of the printed circuit strip and in substantially coaxial alignment. An end of the circuit strip extends beyond the cover panel to expose terminals thereon for connection to a camera. Typically the diameter of the lamps, the width of the printed circuit strip and the width of the channel and the housing member are nearly equal.
The linear photoflash array of the aforementioned copending application Ser. No. 072,251 attains significant economy of manufacture through the use of a single integral component as both the reflector member and the rear housing of the unit, thereby eliminating a separate base or rear housing member. Further economy of manufacture is realized by the use of essentially full metalization of the reflector housing member as an electrostatic shield for the circuit board and lamps carried internally thereof thereby eliminating the need for separate cost increasing shields. These and other aspects contributing to the integrality of construction, product simplicity and economy of manufacture result in a more cost-effective and pocketable unit and facilitates the practical marketing of separate arrays custom-tailored to the now-divergent needs of conventional and instant picture systems. For example, using the same basic construction, the unit can be dimensioned to provide double-ended arrays having three comparatively lower output flashlamps in each half of the units (a total of six lamps) for use with conventional cameras employing high speed film, or the unit can be figured to provide a double-ended array of two higher output lamps associated with larger reflectors in each half of the array (a total of four lamps) for use with instant picture cameras. In each case, the overall length of the unit would be approximately the same or slightly larger than the flipflash units mentioned hereinbefore.
In view of the extreme compactness of the above-described linear array, with the lamps positioned extremely close to one another along an open channel, with reflective sidewalls, the possibility of undesired sympathetic ignition of adjacent lamps becomes a much more significant problem. The compactness of the array must be maintained to deliver the pocketable package size which is more attractive to the customer. This eliminates the option of making the unit larger so that the lamps are further apart. The lamps also cannot be separated by reflector walls because such configuration would also undesirably increase the size of the array. Further, the use of a plurality of individual partition members secured to the rear housing member by wedging them into slots provided therein, such as disclosed in the aforementioned U.S. Pat. No. 4,055,759 relating to a signal device, is inconsistent with the aforementioned objectives of integrality of construction, product simplicity, economy of manufacture, cost-effectiveness and pocket-sized compactness.